The concept of G-force measurement and instrumentation itself is not new. For years there have been instruments utilized in aircraft and spacecraft to measure and display the G-forces applied in both vertical and lateral movements. The application of this technology to the automotive industry has to some extent been limited. For several years, there have been devices on the market employing G-force measurement as a means to accomplish various automotive related functions such as shock and vibration testing, skid pad testing, crash testing, anti-theft alarms as well as other functions.
Although integrated circuit accelerometers have been utilized in some automotive applications, a tremendous untapped potential exists for the implementation of such devices into the field of automotive instrumentation. Current automotive technology provides a variety of instruments which help a driver monitor the performance and condition of the vehicle. Automotive speedometers and tachometers are two such devices which have been in use for decades. The information provided by these devices is extremely limited. A speedometer merely provides the speed of the vehicle; a tachometer merely provides the revolutions per minute (RPM) of the vehicles power plant. Neither of these devices provide the driver of a vehicle an accurate, instantaneous readout of the vehicle's ability to accelerate or decelerate; nor do they provide a means of accurately analyzing changes made to a vehicle which may affect the acceleration or deceleration performance of the vehicle. The acceleration or deceleration performance of a vehicle is best measured by an accelerometer or G-force measuring device.
G-force measuring devices, of the type disclosed in U.S. Pat. No. 3,318,157 entitled "Acceleration-Deceleration Indicator" issued May 9, 1967 to I. Browning et al; U.S. Pat. No. 4,051,734 entitled "G-METER issued Oct. 4, 1977 to Skinner and U.S. Pat. No. 4,807,475, entitled "Accelerometer" issued Feb. 28, 1988 to W. B. Graham are representative of accelerometers having pendulum-type acceleration sensitive elements.
The pendulum-type accelerometers are inherently inaccurate since the mass of the gears, shafts, pointers and any other moving parts will alter the result of the equation F=Ma due to the effect of force resistance. Also, the weight of the shaft of the pendulum may be proportionately small compared to the mass of the weight on the end of the pendulum arm but should not be ignored. Wear on the mechanical components will cause inaccuracies; as will stray lateral forces acting on the pendulum weight.
U.S. Pat. No. 4,430,895 entitled "Piezoresistive Accelerometer" issued Feb. 14, 1984 to R. F. Colton and U.S. Pat. No. 4,622,548 entitled "Solid State Electronic G-Force Indicator" issued Nov. 11, 1986 to J. R. Andres et al disclose acceleration sensing transducers for use in accelerometers that are a substantial improvement over pendulum-type accelerometers. Accelerometers using acceleration sensing transducers are more reliable and have smaller size, smaller mass and greater accuracy.
It is an object of the present invention to implement integrated circuit accelerometers into the field of automotive instrumentation.
It is a further object of the present invention to provide instrumentation that provides the driver of a vehicle an accurate, instantaneous readout of the acceleration or deceleration of the vehicle.
It is a further object of the invention to provide instrumentation for accurately analyzing changes made to a vehicle that may affect its acceleration or deceleration performance.
It is yet a further object of the present invention to apply accelerometer technology to automotive instrumentation that will permit the vehicle operator to monitor the performance of the vehicle braking system and the compression ratio of an engine coupled to a standard transmission engine, both of which have a direct bearing on the rate at which the vehicle decelerates when the brakes are applied or the operator's foot is lifted off the accelerator.
It is further object of the invention to provide a G-meter that may be configured to measure G-force values ranging from as little as plus or minus 0.1 g to as great as plus or minus 500 g's by simply changing the value of the sensitivity on the transducer element and recalibrating the instrument.
It is yet a further object of the invention to include electrical current means for providing an output to a computer system or chart recording device for data analysis.
It is yet a further object of the invention to incorporate in the accelerometer instrumentation a tachometer function.
These and other objects of the invention will be apparent from the following disclosure of a preferred embodiment of the present invention.